Help, how to deal with high-frequency power supply noise mixed in the audio signal waveform

kaka009

Help, how to deal with high-frequency power supply noise mixed in the audio signal waveform [Copy link]

I have been working on a similar audio amplification solution recently. The op amp directly outputs a waveform within the range of 0-1V. After testing the basic functions, I encountered a problem that the audio signal became coarser. After amplification, I found that high-frequency noise was mixed in. Through periodic calculation, the frequency is about 350KHz, which happens to be the frequency of the DCDC switching power supply. 10nf and 0.1uf capacitors were added to the output of the op amp, but they did not have much effect. The power supply ripple was tested alone and was about 30mVpp. The key is whether there is any way to get rid of this power supply frequency. The effective signal is between 100-30KHz and the noise is at 350KHz. Because the op amp cannot be rail-to-rail, positive and negative power rails are required, otherwise part of the 0V will be clipped. Please give me some advice and guidance.

S3S4S5S6

Add a large capacitor to the DC/DC input, and connect the output to the CLC Π-type filter. L can be appropriately larger.

maychang

In this case, you should first determine whether the noise is introduced from the power line or the input end of the audio amplifier circuit. Then add a low-pass filter where the noise enters.

lanhua

The key is whether there is any way to get rid of this power frequency:

I wonder if “shielding” is effective?